I have compared results of different shell-model calculations for the low-lying states of ${}^{16}$C. Comparisons include excitation energies, neutron occupancies, calculated matter radius of ${}^{16}$C, and the energy difference between mirrors ${}^{16}$C and ${}^{16}$Ne. I find that an older, simple calculation produces quite good agreement with experimental quantities.

Photons from the interaction of a highly energetic jet with a thermal medium are an important contribution to the total photon yield measured in ultrarelativistic heavy-ion collisions and also an important probe to study the medium degrees of freedom. Previously this contribution has often been computed in the context of a leading parton energy loss approximation. In this work, jet-medium interaction photons are instead estimated using a medium-modified shower evolution model, where the energy degradation due to vacuum radiation prior to medium formation, the virtuality evolution of intermediate states, and the photon emission from subleading shower partons are taken into account consistently. The results indicate that the leading parton energy loss approximation does not appear to work well for photon emission from jet-medium interaction.

Four high-spin collective bands have been populated in ${{}_{68}^{154}\mathrm{Er}}_{86}$ via the ${}^{110}\mathrm{Pd}({}^{48}\mathrm{Ti},4n\gamma ){}^{154}\mathrm{Er}$ reaction. Average transition quadrupole moments $Q_{\mathrm{t}}$ have been measured for three of the bands by using the Doppler-shift attenuation method. The strongest band has a value of $Q_{\mathrm{t}}=11.0\pm 1.0e\mathrm{b}$, similar to values found recently for four triaxial strongly deformed (TSD) bands in ${}^{157,158}\mathrm{Er}$. The second band has a value of $Q_{\mathrm{t}}=19.5\pm 3.2e\mathrm{b}$, consistent with a predicted axially symmetric superdeformed (SD) shape, similar in deformation to the ${}^{152}\mathrm{Dy}$ isotone, and is used as a calibration point. The third, new band has a value of $Q_{\mathrm{t}}=9.9\pm 2.2e\mathrm{b}$. The results confirm the unexpectedly large $Q_{\mathrm{t}}$ moments for the favored TSD bands in light erbium isotopes.

Background: Neutron-skin thickness is an excellent indicator of isovector properties of atomic nuclei. As such, it correlates strongly with observables in finite nuclei that depend on neutron-to-proton imbalance and the nuclear symmetry energy that characterizes the equation of state of neutron-rich matter. A rich worldwide experimental program involving studies with rare isotopes, parity-violating electron scattering, and astronomical observations is devoted to pinning down the isovector sector of nuclear models.

Purpose: We assess the theoretical systematic and statistical uncertainties of neutron-skin thickness and relate them to the equation of state of nuclear matter, and in particular to nuclear symmetry energy parameters.

Methods: We use the nuclear superfluid density functional theory with several Skyrme energy density functionals and density dependent pairing. To evaluate statistical errors and their budget, we employ the statistical covariance technique.

Results: We find that the errors on neutron skin increase with neutron excess. Statistical errors due to uncertain coupling constants of the density functional are found to be larger than systematic errors, the latter not exceeding 0.06 fm in most neutron-rich nuclei across the nuclear landscape. The single major source of uncertainty is the poorly determined slope $L$ of the symmetry energy that parametrizes its density dependence.

Conclusions: To provide essential constraints on the symmetry energy of the nuclear energy density functional, next-generation measurements of neutron skins are required to deliver precision better than 0.06 fm.

We calculate the toroidal quadrupole moment and form factor of the deuteron, which violate time-reversal symmetry but conserve parity, at leading order in two-flavor chiral effective field theory with perturbative pion exchange. We take into account time-reversal and parity violation owing to the QCD vacuum angle combined with parity violation resulting from the weak interaction in the Standard Model. We also consider time-reversal and parity violation that at the quark-gluon level results from effective dimension-six operators originating from physics beyond the Standard Model.

Giant multipole resonances in Nd and Sm isotopes are studied by employing the quasiparticle-random-phase approximation on the basis of the Skyrme energy-density-functional method. Deformation effects on giant resonances are investigated in these isotopes, which manifest a typical nuclear shape change from spherical to prolate shapes. The peak energy, the broadening, and the deformation splitting of the isoscalar giant monopole (ISGMR) and quadrupole (ISGQR) resonances agree well with measurements. The magnitude of the peak splitting and the fraction of the energy-weighted strength in the lower peak of the ISGMR reflect the nuclear deformation. The experimental data on ISGMR, isoscalar giant dipole (ISGDR), and ISGQR are consistent with the nuclear-matter incompressibility $K\simeq 210–230$ MeV and the effective mass $m_0^{*}/m\simeq 0.8–0.9$. However, the high-energy octupole resonance (HEOR) in ${}^{144}$Sm seems to indicate a smaller effective mass, $m_0^{*}/m\simeq 0.7–0.8$. A further precise measurement of HEOR is desired to determine the effective mass.

The reaction dynamics of various odd-mass Fr isotopes is studied over a wide range of incident energies, spread across the Coulomb barrier. The specific reactions analyzed are ${}^{18}$O+${}^{197}$Au and ${}^{19}$F+${}^{192,194,196,198,200}$Pt, forming odd-mass ${}^{211-219}$Fr${}^{*}$ compound systems where some data are available for three of these isotopes: ${}^{213,215,217}$Fr${}^{*}$. Based on the dynamical cluster-decay model (DCM), we have extended our calculations of the evaporation residue (ER) cross sections to the mainly fissioning ${}^{215}$Fr${}^{*}$, using the systematics of ${}^{213,217}$Fr${}^{*}$ isotopes where the available ER cross sections (as well as fusion-fission cross sections) were studied earlier within the DCM. In order to obtain a clear picture of the dynamics involved, including entrance channel effects, the variations of fragmentation potential, preformation factor, and decay barrier height are analyzed. The relevance of barrier modification effects is also explored in the decay of ${}^{213,215,217}$Fr${}^{*}$ nuclei. In addition, fusion-fission (ff) cross sections are extended to ${}^{213,217}$Fr${}^{*}$ systems where some more data has recently become available. Also, the fission fragment anisotropies (so far measured and studied for ${}^{215}$Fr${}^{*}$ alone) are estimated for ${}^{213,217}$Fr${}^{*}$ using DCM for the use of nonsticking moment of inertia, and relevant comparison with the sticking moment-of-inertia approach is analyzed. Furthermore, the shell closure effects of the decay fragments are investigated for odd-mass ${}^{211-219}$Fr${}^{*}$ isotopes.

It has been shown in previous work [Kiss et al., Phys. Rev. Lett. 101, 191101 (2008); Rauscher et al., Phys. Rev. C 80, 035801 (2009)] that a suppression of the stellar enhancement factor (SEF) occurs in some endothermic reactions at and far from stability. This effect is re-evaluated using the ground-state contributions to the stellar reaction rates, which were shown to be better suited to judging the importance of excited-state contributions than the previously applied SEFs. An update of the tables shown in the latter work is given. The new evaluation finds 2350 cases (out of a full set of 57 513 reactions) for which the ground-state contribution is larger in the reaction direction with a negative reaction $Q$ value than in the exothermic direction, thus providing exceptions to the commonly applied $Q$ value rule. The results confirm the Coulomb suppression effect but lead to a larger number of exceptions than previously found. This is due to the fact that often a large variation in the g.s. contribution does not lead to a sizable change in the SEF. On the other hand, several previously identified cases do not appear anymore because it is found that their g.s. contribution is smaller than inferred from the SEF.

The neutron-unbound nucleus ${}^{15}$Be was observed for the first time. It was populated using neutron transfer from a deuterated polyethylene target with a 59 MeV/u ${}^{14}$Be beam. Neutrons were measured in coincidence with outgoing ${}^{14}$Be particles and the reconstructed decay energy spectrum exhibits a resonance at 1.8(1) MeV. This corresponds to ${}^{15}$Be being unbound by 0.45 MeV more then ${}^{16}$Be thus significantly hindering the sequential two-neutron decay of ${}^{16}$Be to ${}^{14}$Be through this state.

A new numerical method of calculating the Hartree-Fock-Bogoliubov (HFB) and time-dependent HFB (TDHFB) with the Gogny interaction is proposed. The three-dimensional harmonic-oscillator (3DHO) basis functions are replaced by one-dimensional spatial grid points of Lagrange mesh plus two-dimensional harmonic-oscillator basis functions in the perpendicular plane to the direction of the spatial grid points [Lagrange mesh and harmonic oscillator (LMHO)]. By using the LMHO, the calculations of the HFB and TDHFB are carried out in the typical nuclei of ${}^{20}\mathrm{O}$ and ${}^{34}\mathrm{Mg}$ as an illustration of the feasibility of the TDHFB formulation with the LMHO. The strength functions of the quadrupole vibrations ($K=0$) are obtained and are compared with the ones calculated with the 3DHO.

We formulate the finite-temperature relativistic Hartree-Bogoliubov theory for spherical nuclei based on a point-coupling functional, with the Gogny or separable pairing force. Using the functional PC-PK1, the framework is applied to the study of pairing transitions in Ca, Ni, Sn, and Pb isotopic chains. The separable pairing force reproduces the gaps calculated with the Gogny force not only at zero temperature, but also at finite temperatures. By performing a systematic calculation of the even-even Ca, Ni, Sn, and Pb isotopes, it is found that the critical temperature for a pairing transition generally follows the rule $T_c=0.6{\Delta }_n\left(0\right)$, where ${\Delta }_n\left(0\right)$ is the neutron pairing gap at zero temperature. This rule is further verified by adjusting the pairing gap at zero temperature with a strength parameter.

We study the nuclear transparency $T$ for the exclusive reaction ${\gamma }^{*}+A\to \rho +p+{(A-1)}^{*}$ at incident virtual photon energies $\nu ⩾$ 10 GeV to investigate the separate dependence on the photon virtuality, $Q^2$, and the four-momentum transfer squared to the knocked-out proton, $t$. If the effects of color transparency are included, $T$ shows significant variation with $t$ even for small values of $Q^2$ for fixed values of the coherence length $l_c$, and also shows significant increase as $Q^2$ is increased at fixed $l_c$ and $t$. The value of $T$ is found to depend strongly on the phase space over which it is measured.

Temperature dependence of the surface thickness parameter $b$ in the original version of proximity formalism is investigated by including the modification effects of equation of state (EOS) at finite temperature on nuclear potential. Here, this modification is performed using the evaluation of the increasing of total energy in the overlapping region by the EOS extracted from the extended Thomas-Fermi approach for asymmetric nuclear matter at finite temperature. This EOS is also supplemented with the saturation effects of nuclear matter density. Our results show a different temperature dependence for surface thickness $b$ of the excited compound nucleus, which is formed during the fusion process. The original version of Proximity 77 with this new form of $b\left(T\right)$ provides a reasonable result for theoretical values of the barrier characteristics and fusion cross section. Our obtained results are also compared with other theoretical approaches.

The energy-dependent real and imaginary parts of the optical potential of some twenty pairs of spin-unsaturated, open $j$-shell nuclei are calculated in the energy density model, using the complex Skyrme III energy density. The calculated potentials, without any renormalization, reproduce the experimental data on elastic scattering cross sections of all the pairs of nuclei studied. The contribution of the spin density terms, of the Skyrme III energy density, toward such potentials and toward the corresponding elastic scattering cross sections and sub-barrier fusion cross sections are investigated.

Elliptic flow of direct photons in relativistic heavy ion collisions is believed to be dominated by contribution from thermal radiation of quark gluon plasma up to $p_T\sim 5$ GeV/$c$, although other sources start outshining the thermal contribution at already smaller values of $p_T$ in the direct photon spectrum. The elliptic flow of thermal photons from ideal hydrodynamics considering a smooth initial density distribution underpredicts the PHENIX direct photon data from $200A$ GeV Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) by a large margin in the range $1<p_T<5$ GeV/$c$. However, a significant enhancement of thermal photon production due to fluctuations in the initial QCD matter density distributions is expected. We show that such fluctuations result in substantially larger photon elliptic flow for $p_T>2.5$ GeV/$c$ compared to a smooth initial-state-averaged density profile. The results from event-by-event hydrodynamics are found to be sensitive to the fluctuation size parameter. However, the effects of initial state fluctuations are insufficient to account for the discrepancy to the PHENIX data for direct photon elliptic flow. Furthermore, the photon $v_2$ is reduced even more when we include the NLO pQCD prompt photon component. We also calculate the spectra and elliptic flow of thermal photons for 2.76A TeV Pb+Pb collisions at the Large Hadron Collider (LHC) and for the 0–40% centrality bin. Thermal photons from event-by-event hydrodynamics along with prompt photons from NLO pQCD calculations explain the ALICE preliminary direct photon data well in the region $p_T⩾2.5$ GeV/$c$. Similar to RHIC, the elliptic flow results at LHC are again found to be much smaller than the ALICE preliminary $v_2$ data.

We explain the low-energy anomaly reported in several experimental studies of the radiative dipole strength functions in medium-mass nuclei. These strength functions at very low $\gamma$ energies correspond to the $\gamma$ transitions between very close nuclear excited states in the quasicontinuum and attract an increasing interest because of their substantial astrophysical impact. We show that the low-energy enhancement of the strength functions in highly excited compound nuclei is explained by nucleonic transitions from the thermally unblocked single-quasiparticle states to the single-(quasi)particle continuum. The case of radiative dipole strength functions at the nuclear excitation energies typical for the thermal neutron capture is illustrated for ${}^{94,96,98}$Mo and ${}^{116,122}$Sn in comparison to available data.

A new angular momentum projection for systems of particles with arbitrary spins is formulated based on the Heine-Stieltjes correspondence, which can be regarded as the solutions of the mean-field-plus -pairing model in the strong-pairing interaction $G\to \infty$ limit. Properties of the Stieltjes zeros of the extended Heine-Stieltjes polynomials, whose roots determine the projected states, and the related Van Vleck zeros are discussed. An electrostatic interpretation of these zeros is presented. As examples, applications to $n$ nonidentical particles of spin $1/2$ and to identical bosons or fermions are made to elucidate the procedure and properties of the Stieltjes zeros and the related Van Vleck zeros. It is shown that the new angular momentum projection for $n$ identical bosons or fermions can be simplified with the branching multiplicity formula of U$\left(N\right)\downarrow \mathrm{O}\left(3\right)$ and the special choices of the parameters used in the projection. Especially, it is shown that the solutions for identical bosons can always be expressed in terms of zeros of Jacobi polynomials. However, unlike nonidentical particle systems, the $n$-coupled states of identical particles are nonorthogonal with respect to the multiplicity label after the projection.

Background: Low-lying octupole collective excitations play an important role in the description of the structure of nuclei in the actinide region. Ground state alternating parity rotational bands combining both positive and negative parity states are known in several nuclei. However, only recently it has been discovered in ${}^{240}$Pu an excited positive parity rotational band having an octupole nature and demonstrating strong anharmonicity of the octupole motion in the band head energies.

Purpose: To suggest a model describing both ground state and excited alternating parity bands, which includes a description of the anharmonic effects in the bandhead excitation energies and can be used to predict the energies of the excited rotational bands of octupole nature and the $E1$ transition probabilities.

Methods: The mathematical technique of the supersymmetric quantum mechanics with a collective Hamiltonian depending only on the octupole collective variable which keeps axial symmetry is used to describe the ground state and excited alternating parity rotational bands.

Results: The excitation energies of the states belonging to the lowest negative parity and the excited positive parity bands are calculated for ${}^{232}$Th, ${}^{238}$U, and ${}^{240}$Pu. The $E1$ transition matrix elements are also calculated for ${}^{240}$Pu.

Conclusions: It is shown that the suggested model describes the excitation energies of the states of the lowest negative parity band with the accuracy around 10 keV. The anharmonicity in the bandhead energy of the excited positive parity band is described also. The bandhead energy of the excited positive parity band is described with the accuracy around 100 keV.

In mean-field approximation, we study a chiral soliton of the linear sigma model with two flavors at finite temperature and density. The stable soliton solutions are calculated with some appropriate boundary conditions. Energy and radius of the soliton are determined in a hot medium of constituent quarks. It is found that, for $T<T_c$, the energy of the soliton, $E^{*}$, is less than the energy of three free constituent quarks, $3M_q$, but with increasing temperature the difference between $E^{*}$ and $3M_q$ becomes smaller and smaller. Once $T>T_c$, there is a sharp delocalization phase transition from hadron matter to quark matter coincident with the restoration of chiral symmetry. In the transition region, the thermodynamic properties show large discontinuities which is an indication for a first-order phase transition.

${}^{192}$Pt is produced solely by the slow neutron capture ($s$) nucleosynthesis process and hence an accurate ($n,\gamma$) reaction rate for this nuclide would allow its use as an important calibration point near the termination of the $s$-process nucleosynthesis flow. For this reason, we have measured neutron capture and total cross sections for ${}^{192,194,195,196,\mathrm{nat}}$Pt in the energy range from 10 eV to several hundred keV at the Oak Ridge Electron Linear Accelerator. Measurements on the other Pt isotopes were, in part, necessitated by the fact that only a relatively small ${}^{192}$Pt sample of modest enrichment was available. Astrophysical ${}^{192,194,195,196}$Pt($n,\gamma$) reaction rates, accurate to approximately 3%–5%, were calculated from these data. No accurate reaction rates have been published previously for any of these isotopes. At $s$-process temperatures, previously recommended rates are larger (by as much as 35%) and have significantly different shapes as functions of temperature than our new rates. We used our new Pt results, together with ${}^{191,193}$Ir($n,\gamma$) data, to calibrate nuclear statistical model calculations and hence obtain an improved rate for the unmeasured $s$-process branching-point isotope ${}^{192}$Ir.